The present invention relates to an apparatus for initially adjusting the narrow sides of an adjustable mold and for subsequently continually monitoring the inclination and adjusting the same in dependence upon casting parameters in order to maintain, for instance, a particular level of the molten material in the mold.
It is well known that during continuous casting of relatively wide slabs, the casting shrinks in the wide direction during traversal of the mold and in dependence upon the casting speed. For instance, the shrinkage amounts to approximately 0.9% of the casting width for a casting speed of one meter per minute. In order to offset this shrinkage in the mold, it has been practiced to position the narrow sides of the casting mold at a downwardly tapering inclination amounting to a narrowing of the long width of the mold cavity in the direction of casting. The adjustment of the inclination of the sides of the mold is customarily carried out on the basis of empirically obtained parameters and, once adjusted, that inclination is usually not changed during the casting process. This procedure is definetely a disadvantage because the casting speed as a whole is not constant; rather, the casting speed in the beginning as well as at the end amounts to only approximately 15% of the normal mean casting speed observed during steady-state operation. Moreover, if for any reason the inclination (tapering) or reduction in a mold cavity cross section is too large, the friction between casting and mold will increase unduly, causing fissures and cracks to appear in the cast product. If the mold sides are insufficiently inclined, i.e., if they are almost vertically oriented, a gap may form in the lower portion of the mold which will immediately impede the heat transfer from the casting into the mold side which, in turn, causes the casting to be insufficiently cool and the skin which forms in the mold is insufficient to support the casting in its entirety once the casting has left the mold. If the skin, at this point, is too thin, it may readily rupture, particularly when the casting is veered into the horizontal, and the hot metal in the interior may run out.
It can, thus, be seen that, in order to avoid the aforementioned deficiencies, it is necessary to match the inclination of the small sides to the various requirements of the casting during the various phases thereof in order to compensate for the variable shrinkage of the casting throughout the casting process. It is known to adjust the inclination of the narrow sides of the mold for continuous casting on the basis of the heat throughput through these mold sides; for instance, the inclination is increased when, in the lower portion of the mold, the amount of heat transferred into the mold side drops. This approach, however, is disadvantaged by the fact that only the gap formation or the absence thereof can be ascertained. There is very little change in heat transfer if the lower portion of the mold side appears to be, more or less, forced against the passing casting or just engages it. In other words, using heat throughput as a measuring parameter will not indicate too severe a reduction of the mold cross section. Furthermore, ascertaining the tendency of the formation of the gap between the mold side and the casting can temporarily be interfered with if water enters that gap and, at least temporarily, bridges it.